Ribbed underground storage tank



FIG. 1 is a perspective view of a ribbed underground storage tank illustrating my new design;

FIG. 2 is a front elevational view of the ribbed underground storage tank shown in FIG. 1, the left, right and rear elevational views being mirror images;

FIG. 3 is a top plan view of the ribbed underground storage tank shown in FIGS. 1 and 2; and,

FIG. 4 is a bottom plan view thereof. 

The ornamental design for a ribbed underground storage tank, as shown and described. 